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The material

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Earth is an ancient and widespread building material. Thousands of examples from world architecture testify of its use on all continents during the development of human civilizations.

DISTRIBUTION

In Bulgaria
Until the middle of the XXth century earth was used in Bulgaria in association with wood and stone as the main building material. The most widespread techniques are daubed earth, adobe brick and all their variations.

Map of the places in Bulgaria where earth buildings can be found

 

 

 

 

Globally
As it is easily available, right under our feet, earth is among the first materials used by Man for building purposes. It has attended the development of ancient civilizations in Mesopotamia, Egypt, Latin America and Africa.

The adobe brick is the oldest prefabricated building element. Blocks were prepared during springtime in the river valleys, let to dry and used for building purposes during times convenient for the families and the population. Many ancient cities are mainly built of earth.

The city of Shibam in Yemen is an example of such a habitat that has crossed the centuries and has preserved its authentic aspect until our times. The buildings reach 30 meters in height (8 floors) and are an example of a building technology that is compact and respectful of the environment.

Map of the places globally where earth buildings can be found

 

 

 

 

 
PROPERTIES

Modern times
Forgotten in the middle of the XXth century, earth has been rediscovered in the developed countries as a material with great potential during the first petrol crisis in 1973. It then represented an interesting alternative to the energy consuming techniques as the burnt brick or the steel reinforced concrete. Its thermal qualities make it particularly adapted for use in ecological or bioclimatic projects. Today earth is more and more often used in combination with other natural materials for the confection of beautiful, comfortable and healthy dwellings and public buildings.

Availability:
Earth is one of the most widespread materials on our planet. It is produced by the erosion of the planet’s rocky mantel by various mechanical and chemical processes. Locally different in constituents and qualities, it is used for building purposes on all continents and geographical latitudes except the poles and the sandy desert regions.

Low embodied energy: 
Earth has a particularly short production cycle. It is often extracted close to the building site or transported via short distances. The surface on which we walkis dug out and the top layer, rich in humus and variable in thickness (2cm to 2m), is carefully removed. The underlying layer is the one adapted for building purposes.

This second layer is dug out and sieved, if necessary. Depending on the building technique with which it will be used, the earth is mixed with water and/or plant fibers andplaced in a mold, a frame or on a lattice structure and let to dry. In this way very little energy is used in comparison to other techniques that require transport and firing..

For comparison:
Embodied energy in 1m2

Material Energy MJ/kg Density kg/m3
Rammed earth wall 0,45 1460/1800
Cement wall 1,11 2400
Brick wall 3 1700

Easy to recycle: 
If not stabilized with lime or cement, earth can be recycled endlessly. This property brings it to one of the first places among natural building materials.

Storing Heat:
Earth is a massive material. Its density is comparable to that of stone (1800-2200 kg/m3). and is thus conducting energy. Dependent on the thickness of the building element that it constitutes, it can transfer the solar or heat energy with several hours of interval and regulate the thermal differences between day and night.

Regulating humidity: 
One of the constitutive elements of earth – clay – is strongly reactive to water/humidity. Walls made of earth can store a big quantity of humidity and then restitute it without losing their holding capacities. Humidity in a given room is thus regulated, which improves the comfort of the inhabitants and avoiding the apparition of condensation and mould.

Beautiful and colorful:
Earthen tones are natural, non intrusive and warm. The material offers a wide palette of colors, spreading from white and yellow to dark brown and gray, passing trough oranges, reds, greens. Their use creates a cozy interior.

Fire-resistant and insect-protection: 
Earth is a material that doesn’t burn. It does often protect timber structures form direct contact with fire as well as insects.

Pleasant to use:
Earth is an extremely gratifying material. To achieve the plasticity necessary for work only water and plant fibers are added. There is no irreversible chemical reaction (as with lime or cement) which makes earthen materials pleasant to the skin and the hand can often replace tools without worries for burns or hurts.

USE

Adobe block 
Adobe blocks are made of earth mixed with water (sometimes with added plant or animal fibers, for example cut straw), shaped in a mold and sun-dried. Molds can have different dimensions and shapes.

Daubed wall
The daubed wall is built from earth, mixed with water and plant or animal fibers, shaped over a fence placed between a supporting timber structure.

Rammed earth
Rammed earth is a building technique that uses earth compacted in consecutive layers between wooden or metal formworks with the help of a wooden or pneumatic mallet.

Compressed earth blocks
This technique is relatively new. It combines elements of the adobe block (the mold) and the rammed earth technique (the compaction). Earth is compacted manually or mechanically and is necessarily stabilized with lime or cement (from 2 to 5%).

Cob
A building technique where earth is mixed with plant or animal fibers and water and is manually shaped in consecutive layers of 50-60cm height. The walls are rectified – vertically cut, after the mixture has dried lightly (usually 24 hours later). The built walls are supporting and their thickness varies between 50 and 70cm.

Mixed techniques 
Building techniques where earth is mixed with plant elements (cut straw, saw-dusts, hemp fibers…) and is placed between supporting elements.

Plastering
Building technique where earth is mixed with water (and depending on the case with plant or animal fibers) and applied as a thin layer (2mm to 5cm) on a wall to improve its esthetical and physical properties.

Floors
Earth is often used for the confection of floor deckings in rural houses. It is applied on a thin layer as a plaster and is refurbished at least once a year.